1. Field of the Invention
The present invention relates to a lens-fitted photo film unit. More particularly, the present invention relates to a lens-fitted photo film unit pre-loaded with a photo film cassette, and of which the photo film cassette being removed after exposures can be safely handled.
2. Description Related to the Prior Art
There is a lens-fitted photo film unit pre-loaded with a photo film, and provided with a simple construction for taking exposures. The photo film is contained in the lens-fitted photo film unit in a state where a trailing end of the photo film is secured to a spool. The spool is contained in a cassette in a rotatable manner. A winder wheel is connected to the spool, and after each exposure, is rotated to wind an exposed portion of the photo film into the cassette. The cassette can be unloaded from the lens-fitted photo film unit in an illuminated room, not in a dark room. There is a type of the lens-fitted photo film unit in which a cassette shell is formed from resin, contains the photo film, and in which an operation of inserting the photo film into the lens-fitted photo film unit is facilitated.
There is a photo film passageway or mouth, defined along a line between the shell halves, for passage of the photo film between the inside and the outside of the cassette shell. A cassette shutter is contained in an inner position of the passageway, and rotates to open/close the passageway. There are indicator openings formed in one of end faces of the cassette shell where an indicator plate is disposed. The indicator openings are different in the shape, and associated with respective meanings of "Unexposed", "Partially exposed", "Exposed" and "Developed" statuses of the photo film. The indicator plate with the spool rotates in its position behind the indicator openings inside the cassette shell, and is stopped in any one of the indicator openings. One meaning associated with one of the indicator openings through the indicator plate is visible implies the status that the photo film has in the cassette shell.
After taking exposures in all of the available frames, a user forwards the lens-fitted photo film unit to a photo laboratory and requests photo finishing of the photo film. A photofinishing operator of the photo laboratory removes the cassette from the lens-fitted photo film unit. Before the cassette is removed from the lens-fitted photo film unit, the winder wheel is checked by applying rotary force to it by the operator. This is because it should be confirmed that the entirety of the photo film has been wound into the cassette shell. Since this cannot be confirmed by observing the appearance of the lens-fitted photo film unit, rotary force is manually applied to the winder wheel for the confirmation. There is, however, a problem in that such a manual operation is very slow and inconsistent with high efficiency in the photofinishing operation.
In a camera for use with the cassette, there is a photo sensor for detecting a rotational position of the spool. To remove the cassette from the camera, the indicator plate is controlled to stop behind the indicator opening indicating the "Exposed" status. This is for the purpose of avoiding erroneously reloading a camera with the cassette being used. However the lens-fitted photo film unit does not have such a construction for reasons of cost, a space for incorporation and the like. The indicator plate of the cassette removed from the lens-fitted photo film unit is not in a predetermined position. If a user unloads the cassette being used from the lens-fitted photo film unit, the indicator plate is likely to stop behind the indicator opening indicating the "Unexposed" status. The user is likely to incorrectly load a camera with the cassette being used.